This invention relates to the field of semiconductor assembly, and more particularly to a method for forming a material comprising at least one of aluminum nitride and titanium aluminum nitride over the surface of a plurality of semiconductor wafers.
In the manufacture of semiconductor devices various uses for aluminum nitride (AlN) and titanium aluminum nitride (TiAlN) have been proposed. AlN has been used, for example, as an insulator and as a heat sink. TiAlN has been used for an adhesion layer and as a conductive layer, and both AlN and TiAlN have been used for diffusion barriers. Aluminum nitride compounds are extremely hard substances thereby making them also useful as etch stop layers.
U.S. Pat. No. 5,783,483 describes a method of forming an aluminum nitride layer by first depositing a thin aluminum layer by sputtering, chemical vapor deposition (CVD) or ion implantation. Next, the aluminum layer is thermally cycled in a nitrogen ambient to form an aluminum nitride barrier layer. An aluminum nitride layer can further be formed in a single step using CVD or reactive sputtering. After formation of a desired layer, aluminum nitride can be patterned using Cl2 or BCl3 gas using reactive ion etching (RIE).
U.S. Pat. No. 5,687,112 describes that titanium aluminum nitride may be deposited by such methods as physical vapor deposition including evaporation, ion plating as well as by DC and RF sputtering deposition, chemical vapor deposition, and plasma assisted chemical vapor deposition. The exact method used depends upon many factors, for example deposition temperature constraints imposed by the composition of the target material.
Prior methods of forming TiAlN and AlN include formation of the material on a single wafer. Single wafer processing is known to be time consuming and therefore expensive, but a process to form a layer of TiAlN or AlN simultaneously over a plurality of wafers has not been feasible as prior precursor technology has not been viable with only thermal decomposition. In addition to costs added from long processing times, single wafer processing is expensive because additional equipment must be purchased to provide adequate manufacturing throughput. Further, previous methods of forming AlN or TiAlN result in layers having varying thickness over device features, for example thinning at the edges of features, which can decrease device performance and yields. A method for forming TiAlN and AlN on two or more wafers simultaneously which also can improve step coverage would increase production throughput, decrease costs, and improve device performance and yields, and would therefore be desirable.
The present invention provides a new process for forming a layer comprising one of aluminum nitride and titanium aluminum nitride over a semiconductor substrate assembly. The process decreases the time and cost of wafer manufacture and increases wafer throughput by allowing for the simultaneous processing of multiple wafers. In accordance with one embodiment of the invention, at least two wafers are placed into a diffusion furnace. With the wafers in the furnace, a precursor comprising at least one of triethylaluminum and trimethylethylenediamine tris(dimethylamino)titanium is placed into the diffusion furnace. The temperature of the wafers is increased and a layer comprising at least one of aluminum nitride and titanium aluminum nitride is simultaneously formed over a surface of each wafer.
Thus the instant process allows for the formation of a layer comprising one of a titanium aluminum nitride layer and an aluminum nitride layer over the surfaces of two or more wafers simultaneously thereby increasing throughput over conventional single wafer processing.
Other objects and advantages will become apparent to those skilled in the art from the following detailed description read in conjunction with the appended claims and the drawings attached hereto.